Monolithically integrated optical waveguide technology provides key components of recent and expected future improvements in telecommunications and other networks. Optical fiber networks are used to convey data in almost all applications where data rates exceed 1 Gb/sec and transmission distances exceed a few meters. Fiber optic networks pervade and enable the networks forming the internet. There are many different technologies for integrated optics, but for interfacing to fiber networks the clear preference and predominant technology is buried-channel silica waveguides on mechanical substrates of silicon or quartz. This class of waveguide circuitry is generally called planar lightwave circuits, or ‘PLC’.
Coupling light in and out of PLCs is accomplished by routing the appropriate waveguides to the edge of the PLC substrate and mating optical fibers, photo detectors, or lasers to the waveguides at the substrate edges. The waveguides are defined within a single layer of the PLC and are allowed to cross, but practical waveguide crossings do exhibit small amounts of loss and crosstalk and that does add up for multiple crossings, so it is generally desirable to keep the number of crossings for any optical path to be less than the order of 10. Also, optical cores cannot be bent too sharply, minimum radius of curvature allowed is generally a few millimeters. Because of these limitations, the need to route all the access waveguides to the edge of the PLC chip substantially increases the required size of the chip and/or limits the complexity of the optical design.
Thus, a need still remains for better methods of coupling optical fibers to PLCs. In view of the increasing importance of optical data transmission, it is increasingly critical that answers be found to these problems. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems. Additionally, the need to reduce costs, improve efficiencies and performance, and meet competitive pressures adds an even greater urgency to the critical necessity for finding answers to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any practicable solutions and, thus, satisfactory solutions to these problems have long eluded those skilled in the art.